Monday, August 22, 2005


Face of a watch, on which time and further functions are displayed by markers (s.), hands (s.), discs or through windows (s.). Normally it is made of a brass—sometimes silver or gold.

Said of watches whose indications are displayed mostly inside an aperture or window (s.) on the dial.

Undrilled jewel, placed on the balance jewel with the tip of the balance-staff pivot resting against its flat surface, to reduce pivot friction. Sometimes used also for pallet staffs and escape wheels.

ENGINE-TURNED, s. Guilloche.

Indication of the difference, expressed in minutes, between conventional mean time and real solar time. This difference varies from -16 to +16 seconds between one day and the other.

Positioned between the train (s.) and the balance wheel and governing the rotation speed of the wheel-train wheels. In today’s horology the most widespread escapement type is the lever escapement. In the past, numerous types of escapements were realized, such as: verge, cylinder, pin-pallet, detent and duplex escapements. Recently, George Daniels developed a so-called “coaxial” escapement.

Engraving on the dial or case of a watch, covered with an enamel layer.

Said of surfaces worked with thin parallel grooves, mostly on dials or case bezels.

Feature combined with chronograph (s.) functions, that allows a new measurement starting from zero (and interrupting a measuring already under way) by pressing down a single pusher, i.e. without stopping, zeroing and restarting the whole mechanism. Originally, this function was developed to meet the needs of air forces.

Hinged and jointed element, normally of the same material as the one used for the case. It allows easy fastening of the bracelet on the wrist. Often provided with a snap-in
locking device, sometimes with an additional clip or push-piece.

FREQUENCY, s. Vibration
Generally defined as the number of cycles per time unit; in horology it is the number of oscillations of a balance every two seconds or of its vibrations per second. For practical purposes, frequency is expressed in vibrations per hour (vph).

GENEVA SEAL, s. Poincon de Geneve.

Bronze and beryllium alloy used for high-quality balances (s.). This alloy assures high elasticity and hardness values; it is non-magnetic, rustproof and has a very reduced dilatation coefficient, which makes the balance very stable and assures high accuracy of the movement.

Abbreviation for Greenwich Mean Time. As a feature of watches, it means that two or more time zones are displayed. In this case, the second time may be read from a hand making a full rotation in a 24-hour ring (thereby also indicating whether it is a.m. or p.m. in that zone).

Harmonic flattened bell in a steel alloy, generally positioned along the circumference of the movement and struck by hammers (s.) to indicate time by sounds. Size and thickness determine the resulting note and tone. In watches provided with minute-repeaters (s.), there are often two gongs and the hammers strike one note to indicate hours, both notes together to indicate quarters and the other note for the remaining minutes. In more complex models, equipped also with en-passant sonnerie (s.) devices, there may be up to four gongs producing different notes and playing even simple melodies (such as the chime of London’s Big Ben).

Decoration of dials, rotors or case parts consisting of patterns made by hand or engine-turned. By the thin pattern of the resulting engravings—consisting of crossing or interlaced lines—it is possible to realize even complex drawings. Dials and rotors decorated in this way are generally in gold or in solid silver.

Steel or brass element used in movements provided with a repeater or alarm sonnerie (s.). It strikes a gong (s.) or bell (s).

Indicator for the analogue visualization of hours, minutes and seconds as well as other functions. Normally made of brass (rhodium-plated, gilded or treated otherwise), but also steel or gold. Hands are available in different shapes and take part in the aesthetic result of the whole watch.

Heart-shaped cam (s.) generally used to realign the hands of chronograph counters.

Valve inserted in the case of some professional diving watches to discharge the helium contained in the air mixture inhaled by divers.

An artificial glass made of a plastic resin.